314 MARINE PRODUCTS OF COMMERCE 



in the United States and Canada, from which fish are shipped, where solid 

 carbon dioxide either is not available or its price is prohibitive for use in such 

 a scheme. 



The Dieco System. The Dieco "Dry-Ice" system for cooling railway refrigerator 

 cars is somewhat similar to the Broquinda system. It was developed by the Dry- 

 Ice Equipment Company of San Francisco, California, and was tried out in road 

 tests in 1947. The main difference between the Dieco and the Broquinda systems 

 is in the means of circulating the secondary cooling liquid. In the Dieco system 

 this liquid is circulated by pressure generated from the gas evolved from the "Dry 

 Ice," which is contained in a small pressure tank in the bunker chamber. The car 

 temperature is controlled by a throttling valve in the liquid line in a manner 

 similar to that in the Broquinda system. 



The Split-Absorption System 



Presumably the split-absorption system as applied to railway refrigerator cars 

 derives its name from the fact that in this application the ordinary continuous 

 absorption operation is "split" into two parts. In the ordinary ammonia absorption 

 plant, it will be recalled, the evaporation, absorption, and recovery of the ammonia 

 go on concurrently, thus making the operation continuous. In the split-absorption 

 system the evaporation and absorption of the ammonia take place on the car and 

 the recovery of the ammonia from the resulting strong ammonia "liquor" (con- 

 centrated water and ammonia solution) takes place in stationary recovery plants, 

 thus making the operation intermittent. 



By "splitting" the operation this way there are no "moving parts" on the 

 refrigerator car. All that are required here are an ammonia storage tank or re- 

 ceiver, connected to cooling coils through a surge drimi and controlling mechan- 

 ism, and an absorber. The operation of this part of the system is extremely simple. 

 Liquid ammonia is admitted through a control valve to the surge drum and the 

 evaporator coils, where it evaporates or boils under the reduced pressure main- 

 tained by the absorber. The ammonia vapor evolved passes through the coils and 

 is absorbed by the water in the absorber. The temperature in the car is con- 

 trolled by a thermostat which regulates the flow of ammonia to the coils and the 

 gas from the coils to the absorber through the pressure in the coils. 



The Frigid Transport Corporation of the United States holds patents covering 

 the split-absorption system on railway cars, and at the request of this corporation 

 and the Birdseye-Snider Division of General Foods Corporation the U. S. De- 

 partment of Agriculture conducted a test of a refrigerator car equipped with 

 this system. The car tested was fitted with two ammonia storage tanks with a 

 combined capacity of 1,900 pounds and two water tanks or absorbers with a 

 total capacity of 750 gallons (Anon., 1947). During a ten-day observation period, 

 a mean temperature of approximately 0° F (— 17.8° C) was maintained inside 

 the car while the outside temperature was held at 92° F (33.3° C). A total of 

 11,000 pounds of ammonia, at the rate of 42 pounds per hour, and 5,000 gallons 

 of water, at 19 gallons per hour, were used. Servicing took place at daily intervals; 

 it involved the addition of about 1,000 pounds of liquid ammonia and the removal 

 of the ammonia solution and its replacement with 500 gallons of fresh water 

 each day. 



The daily servicing requirements, coupled with the disposition of the strong 



